As a conventional metal working machine, there is known an electro-chemical machine in which a gap between a workpiece and an electrode is filled with an electrolyte such as sodium nitrate or sodium chloride, the electrolyte is caused to flow at a high speed so that electrolytic products which would obstruct stable electrolytic action (namely, the soluted metal compound, metal ions, hydrogen gas and the like) are eliminated, and the workpiece is worked or machined by producing a direct current flow from the workpiece to the electrode (refer to Japanese Reference No. 61-71921 or 60-44228, or the like). There is also known an electric discharge machine in which a workpiece and an electrode are arranged in a working fluid such as a kerosene or the like so as to face each other across a small gap, a proper power source is connected to the workpiece and electrode, a spark discharge or transient arc discharge is instantaneously generated between the workpiece and the electrode, and the workpiece is worked by the discharge energy (refer to Japanese Reference Nos. 60-26646 or 60-177819).
However, the former electro-chemical machine has problems in that, particularly when a workpiece is three-dimensionally worked so as to leave a bottom (namely when a workpiece having a three-dimensional surface which includes a concave portion is worked), it is difficult to accurately transfer the shape of the electrode to the workpiece and a highly accurate surface quality cannot be obtained. On the other hand, the latter electric discharge machine has problems in that it is difficult to obtain a good surface roughness and, for instance, it is necessary to manually polish and finish the resulting surface to obtain a mirror surface and the like, and it takes a long time and much labor to finish the surface.
Therefore, the assignee of the present invention has already developed an electro-chemical machine which can solve those problems (see Japanese Patent Application No. 62-27616). According to this electro-chemical machine, in order to eliminate electrolytic products produced in the gap between a workpiece and electrode, electrolyte is pumped by a pump from a clean tank of an electrolyte filtering apparatus provided below a working tank, and this electrolyte is emitted from a jet nozzle arranged to be directed toward the gap, thereby eliminating electrolytic products from the gap.
However, despite emission of electrolyte by such a jet nozzle, when the working surface has a complicated shape it is difficult to uniformly emit the electrolyte to the working surface. The surface portions where electrolytic products were efficiently eliminated have better characteristics than the surface portions where they were not efficiently eliminated. Thus, a difference in working conditions occurs on the working surface and a fringe pattern appears. This is a drawback in that the overall surface quality deteriorates significantly in comparison to simpler surface shapes.